Installation

Shell constructors

LocalShell

Takes no arguments:

spur.LocalShell()

SshShell

Requires a hostname. Also requires some combination of a username,
password and private key, as necessary to authenticate:

# Use a passwordspur.SshShell(hostname="localhost",username="bob",password="password1")# Use a private keyspur.SshShell(hostname="localhost",username="bob",private_key_file="path/to/private.key")# Use a port other than 22spur.SshShell(hostname="localhost",port=50022,username="bob",password="password1")

Optional arguments:

connect_timeout – a timeout in seconds for establishing an SSH
connection. Defaults to 60 (one minute).

missing_host_key – by default, an error is raised when a host
key is missing. One of the following values can be used to change the
behaviour when a host key is missing:

spur.ssh.MissingHostKey.raise_error – raise an error

spur.ssh.MissingHostKey.warn – accept the host key and log a
warning

spur.ssh.MissingHostKey.accept – accept the host key

shell_type – the type of shell used by the host. Defaults to
spur.ssh.ShellTypes.sh, which should be appropriate for most Linux
distributions. If the host uses a different shell, such as simpler shells
often found on embedded systems, try changing shell_type to a more
appropriate value, such as spur.ssh.ShellTypes.minimal. The following
shell types are currently supported:

spur.ssh.ShellTypes.sh – the Bourne shell. Supports all features.

spur.ssh.ShellTypes.minimal – a minimal shell. Several features
are unsupported:

Non-existent commands will not raise spur.NoSuchCommandError.

The following arguments to spawn and run are unsupported unless
set to their default values:
cwd, update_env, and store_pid.

look_for_private_keys – by default, Spur will search for discoverable
private key files in ~/.ssh/.
Set to False to disable this behaviour.

load_system_host_keys – by default, Spur will attempt to read host keys
from the user’s known hosts file, as used by OpenSSH, and no exception will
be raised if the file can’t be read.
Set to False to disable this behaviour.

sock – an open socket or socket-like object to use for communication to
the target host. For instance:

Note that arguments are passed without any shell expansion. For
instance, shell.run(["echo","$PATH"]) will print the literal string
$PATH rather than the value of the environment variable $PATH.

Raises spur.NoSuchCommandError if trying to execute a non-existent
command.

Raises spur.CouldNotChangeDirectoryError if changing the current directory
to cwd failed.

Optional arguments:

cwd – change the current directory to this value before
executing the command.

update_env – a dict containing environment variables to be
set before running the command. If there’s an existing environment
variable with the same name, it will be overwritten. Otherwise, it is
unchanged.

store_pid – if set to True when calling spawn, store the
process id of the spawned process as the attribute pid on the
returned process object. Has no effect when calling run.

allow_error – False by default. If False, an exception
is raised if the return code of the command is anything but 0. If
True, a result is returned irrespective of return code.

stdout – if not None, anything the command prints to
standard output during its execution will also be written to
stdout using stdout.write.

stderr – if not None, anything the command prints to
standard error during its execution will also be written to
stderr using stderr.write.

encoding – if set, this is used to decode any output.
By default, any output is treated as raw bytes.
If set, the raw bytes are decoded before writing to
the passed stdout and stderr arguments (if set)
and before setting the output attributes on the result.

Process interface

pid – the process ID of the process. Only available if
store_pid was set to True when calling spawn.

Has the following methods:

is_running() – return True if the process is still running,
False otherwise.

stdin_write(value) – write value to the standard input of
the process.

wait_for_result() – wait for the process to exit, and then
return an instance of ExecutionResult. Will raise
RunProcessError if the return code is not zero and
shell.spawn was not called with allow_error=True.

send_signal(signal) – sends the process the signal signal.
Only available if store_pid was set to True when calling
spawn.

Classes

ExecutionResult

ExecutionResult has the following properties:

return_code – the return code of the command

output – a string containing the result of capturing stdout

stderr_output – a string containing the result of capturing
stdout

It also has the following methods:

to_error() – return the corresponding RunProcessError. This is
useful if you want to conditionally raise RunProcessError, for
instance:

If the ssh command succeeds, make sure that the arguments to
ssh.SshShell and the ssh command are the same. If any of the
arguments to ssh.SshShell are dynamically generated, try hard-coding
them to make sure they’re set to the values you expect.

I can’t spawn or run commands over SSH

If you’re having trouble spawning or running commands over SSH, try passing
shell_type=spur.ssh.ShellTypes.minimal as an argument to spur.SshShell.
For instance:

This makes minimal assumptions about the features that the host shell supports,
and is especially well-suited to minimal shells found on embedded systems. If
the host shell is more fully-featured but only works with
spur.ssh.ShellTypes.minimal, feel free to submit an issue.

Why don’t shell features such as variables and redirection work?

Commands are run directly rather than through a shell.
If you want to use any shell features such as variables and redirection,
then you’ll need to run those commands within an appropriate shell.
For instance: